I want to replace and old Leviton attic light switch with a Leviton combo switch/outlet. The junction box has two Romex cables in and one out to the current light.

The two in have each a black wire going into to the push-in terminals of the switch and one black one connected to a side screw going to the light. Why would there be two romex cables with two black wires going into the switch? How would I install the combo switch with this wire config? The grounds are just wire nutted together (all three). Thanks for the help.

UPDATE:
Here is a better shot of the back of the old switch with some labels:
CORRECTION... New diagram here:

Based on the updated diagram above... Romex 1 from bottom of box has the shepherd's hook and was attached to the screw... Romex 2 from bottom of box was pushed-in to the bottom of switch... Romex 3 goes to the light through the top of the box from the push-in connection at the top of the switch.

There are 2 Romex running into the bottom of the box... One black going to push-in terminal 1 and the other Romex black going into push-in terminal 2... The 3rd Romex is going to the light... You can see the 2 Romex at the bottom in the photo i.stack.imgur.com/mtwPZ.jpg
– mm-93Jan 27 at 16:16

1

Then Romex 1 must be the line connection, and Romex 2 leads off to something else that is being turned on and off by this switch...can you figure out where that leads?
– ThreePhaseEelJan 27 at 18:41

2 Answers
2

You're in luck!

The fact there are two cables here is a good thing, since it means neutral is available at this box. The wiring here goes as follows:

The always-hot black wires get nutted together and with a black pigtail of appropriate gauge -- this pigtail then goes to a black screw on the switch/receptacle combo

The switched-hot black wire goes to the brass screw on the switch half of the combo

The neutral bundle gets a white pigtail nutted in with it, which goes to the silver screw on the receptacle half of the combo

The ground bundle gets a bare or green pigtail nutted in with it, which goes to the green grounding screw on the device

Once it's all wired up, you can then button things up, turn the power back on, and enjoy your new receptacle!

If you want a switched receptacle

If you want the receptacle to be controlled by the switch, the wiring is actually no harder than an always-hot receptacle. Simply keep the neutral and ground wiring the same, but swap the always-hot and the switched hot so that the always-hot pigtail goes to the brass screw on the switch end and the switched hot goes to one of the black screws.

Is this describing a separate feed where the outlet is always on and the light switch controls the light independently? What if I want to have a common feed where the light switch controls the outlet?
– mm-93Jan 27 at 20:01

@mm-93 -- this is describing a separate feed. Why do you want a switched receptacle here? What are you planning to plug into it?
– ThreePhaseEelJan 27 at 20:03

Just an extension cord for extra lights where I need it in the attic... I’m running CAT6 cable... I just need an outlet to be available in the attic (instead of always running an extension cord from the garage) and don’t care if the switch operates it... in fact the switch will always be turned on when I go up there and turned off when I leave. Is it easier to wire a common feed? (I.e no pigtails needed?)
– mm-93Jan 27 at 20:25

The common feed is easier to wire -- you'd need to break the tab and use a pigtailed jumper if you wanted the outlet to be switched
– ThreePhaseEelJan 27 at 20:43